CubeSat design is facilitated by the increasing availability of open-source software in the domain, and a variety of low-cost hardware blueprints based on commodity microcontrollers. We attain the rock-bottom price to reach orbit as entities that design, launch and operate CubeSats started selling to multiple tenants tiny rack slots (typically 0,25U each) for low-power payloads that may be hosted on their CubeSat. The question arises of how to provide state-of-the-art security for software updates on a multi-tenant CubeSat, whereby mutual trust between tenants is limited. In this paper, we provide a casestudy: ThingSat, a low-power payload we designed, is currently hosted on a CubeSat orbiting at 500km altitude operated by a separate entity. We then design Cubedate, a framework for securing continuous deployment of software to be updated on orbiting multi-tenant CubeSats. We also provide a highly portable open-source implementation of Cubedate, based on the IoT operating system RIOT, which we evaluate experimentally.